An unexpected combination of snappy dialog and darkly slow-burning themes, this unusual drama explores profound issues of faith through an episodic plot and eccentric characters. It's colourful and often hilarious, but it also drags a bit as it circles around its pungent central themes.

Father James (Gleeson) is taken aback when a parishioner tells him in confession that he's going to kill him next Sunday. The next day, his daughter Fiona (Reilly) arrives following another suicide attempt. And he also gets involved with Jack (O'Dowd), who accuses an African neighbour (De Bankole) of beating up his wife (O'Rourke). In addition, there are issues with a local millionaire (Moran), an eccentric old fisherman (Walsh), a grieving French woman (Croze) and an unapologetic convicted murderer (Domhnall Gleeson). Meanwhile, James is trying to make some sense of his own mortality.

Writer-director McDonagh is terrific at writing crackling dialog that distracts us from a story's serious undercurrents. Even darker than The Guard, the mix here is intriguingly subtle, with literate lines spoken by razor-sharp characters. Sometimes this can feel a bit weighty, especially as the slow pacing lulls us into a trance. And sometimes the people feel like deliberately spiky scene-stealers. But the combination is entertaining and ultimately surprising.

Gleeson mutes his sardonic persona intriguingly as a man still traumatised by the death of his wife and the discovery of his vocation as a priest. So his daughter's neediness barely ruffles him. Gleeson's chemistry with Reilly is offhanded and honest, as is the way he deals with the colourful locals, each of whom seems more than a little unhinged. In the superb ensemble, O'Dowd is a standout in a rare menacing role, and the scene between father-son actors Brendan and Domhnall is the show-stopper.

In the end, the lively performances and spectacular scenery hold our interest even as we're mesmerised by the meandering pacing. There's a sense that the script has been written as a fable, with each scene standing in for something much more profound, leading to a conclusion that echoes out in waves of meaning we never see coming. It's a bold approach to storytelling that may alienate some audiences. But it also jolts us into thinking about the fundamental fact that Christianity should be about forgiveness, not sin.